Line Corp. is planning to shake up its staff and business to build on the 20-plus percent share gain since the messaging company pulled off the tech world's biggest public offering of the year.

CEO Takeshi Idezawa is tapping top lieutenants Jun Masuda and Joongho Shin to lead the hunt for fresh growth ideas. Their new responsibilities will be announced as part of a broader revamp of the Tokyo-based company's corporate culture at a town-hall meeting in mid-January, two people familiar with the matter said.

While it might seem strange to alter strategy so soon after July's market debut, subscriber growth is slowing, as is revenue from games and digital stickers. Line is under pressure to come up with new ways to make people spend on what is otherwise a free messaging service. At the same time, it's seeking to expand its user base of 220 million in the face of competition from Tencent Holdings Ltd. and Facebook Inc. Line shares were down less than 1 percent on Wednesday, giving it a market value of ¥888 billion ($7.71 billion).